Vegetative Organs of Vascular Plants 127 



broad apical meristeiii, two siiiall leal pi iinordia, and tragmcnts ol the 

 folded plumule leaves. The radicle can be used for histological 

 or cytological preparations of the growing point. 



Peas show a more advanced condition at a corresponding stage of 

 germination. The pea bud is perfectly glabrous. Sprouts showing 

 axillary bud primordia are obtained when the sprout has emerged 

 from the seed in the form of a loop (Fig. \S.\ D) . Increasing 

 complexity de\elops rapidly as the sprout becomes straight. 



The epicotyl in sprouting soybean is more advanced in organi- 

 zation than in beans or peas. Extract the soybean bud from the burst 

 seed. For an older stage, permit the epicotyl to elongate until the tips 

 of the plumule leaves just protrude beyond the cotyledons. Remove 

 the cotyledons, pull the plumule leaves apart, and remove the entire 

 bud (Fig. 13.1 A-G). Soybean buds are pubescent and must be 

 pumped with an aspirator until they sink in the killing fluid. Large 

 multicellular hairs in the axils of the leaf primordia are easily 

 mistaken for axillary buds by elementary students. The bud is a 

 desirable item for advanced teaching (Fig. 13.4^). The growing 

 point of the flax seedling is glabrous and very simple in organization 

 (Fig. 13.3 d) . When the appressed cotyledons of the seedling have 

 begun to diverge, make a transverse cut 1 nnn. below the cotyledonary 

 node and another cut 2 mm. above the node. The cotyledons serve as 

 a guide to orientation in the microtome. Section at right angles to 

 the flat sides of the cotyledons. 



Axillary buds of Coleiis, tomato, and other herbaceous plants or 

 the buds from potato eyes also are desirable subjects. Before dropping 

 buds of this type into' the killing fluid, it is best to dissect away some 

 of the outer bud scales. 



Uniformly good fixation of buds of the above legumes and other 

 recommended herbaceous plants has been obtained with Craf II and 

 the dioxan method, the ethyl-normal butyl series or the dioxan-normal 

 butyl series. Some good results, with occasional unexplained failures, 

 have been obtained with dioxan alone. 



Buds of trees and shrubs collected at different seasons show the 

 initiation of leaves and flowers, or the dormant condition. Expanding 

 spring buds of the maples, basswood {Tilia glabra) , and tulip poplar 

 (Liriodendron tulipifera) are recommended. In the shrubs, lilac 

 (Syringa) , honeysuckle [Lome era) , and elderberry (Sambiicus) are 

 excellent subjects. Remove the buds from the twig as shown in Fig. 

 13.1 H-J. Slice off a longitudinal slice from each side, peel off some 

 of the tougher outer scales under a magnifier, drop into the killing 



